1. Field of the Invention
The present invention relates generally to the field of chemical compositions for dust suppression and soil stabilization. More specifically, the present invention discloses a chemical composition for dust suppression and soil stabilization that combines an asphalt emulsion with an aqueous magnesium chloride solution.
2. Background of the Invention
A variety of chemical compositions have been used in the past for dust control and suppression, soil stabilization, erosion control, road stabilization and the like—particularly on unpaved roads, construction sites and oilfield sites. But, a single product has not been found that met all of expectations.
Two types of products are commonly used in the field. The first are water-based asphalt emulsions. For example, a water-based cationic asphalt emulsion, commonly known as CCS-1h, is commercially available from many suppliers. It is typically blended as an emulsion containing about 85% water and 15% asphalt and sprayed onto the road surface like a thick coating. It loses its moisture very rapidly with the heat of the sun and from the wicking by the subsurface it is applied to. Traffic must be kept off of the product after spraying for an entire day as the traffic peels up the product on the tires of the vehicles. It must be applied again every seven to ten days as it forms cracks and potholes very quickly even on solidly-built roads. It is usually applied at the rate of about 0.48 gallons per square yard. This product also sits on top of the subsurface and is too thick to penetrate to any significant degree, and peels up very easily although it is a solid surface once it cures.
The other competing family of products in this field employ an aqueous solution of magnesium chloride (MgCl2). For example, one typical formulation consists of magnesium chloride mixed with about 70% water by weight. It is widely used to control dust and also stabilizes the road and dirt and makes the material more solid. This solution is typically applied at a rate of about 0.5 gallons per square yard. The magnesium chloride does chase the water down through the subgrade and is dispersed throughout the subsurface and able to be reworked if more water is added. Magnesium chloride is hydroscopic and pulls moisture from its surroundings (i.e., ground humidity and surrounding material). The problem is that it must be reactivated with more water every few weeks because the salt crystals on the surface dry out and create their own dust that only adds to the problem. It also becomes slick during the wetting process and rain storms.
The prior art in this field also includes U.S. Pat. No. 6,855,754 (Takamura et al.). This patent discloses a paving/coating formulation that includes the combination of: (1) an asphalt emulsion; (2) a water solution of any of a variety of alkali or ammonium salts or hydroxides; and (3) a water solution of any of a variety of metal salts, including Group IIA salts such as magnesium chloride. However, the proportional ranges of ingredients mentioned in the Takamura patent are far outside those of the present invention. The present formulation uses much less asphalt emulsion and more magnesium chloride solution. Also, Takamura is primarily concerned with cold paving with an aggregate. Takamura mentions that the formulation could be used more generally for a coating. However, given the high proportion of asphalt emulsion in the Takamura composition, the result would be a thin surface coating similar to conventional asphalt coatings. In contrast, the present invention is intended for dust suppression by penetrating to a significant depth into the ground, rather than just forming a solid layer on the surface.